The present invention relates to an electric motor comprising a rotor which has a plurality of permanent magnets arranged along a circumferential direction, and a stator arrangement with a winding arrangement which surrounds the permanent magnets, at least in regions.
Electric motors in the form of small drives, which have a low energy consumption, are gaining increasingly in significance. One field of application for such small drives is constituted, for example, by small pump drives and fan drives in automation devices. Furthermore, such small drives are preferably used in medical engineering. Small drives are generally designed for the maximum drive parameters. However, these small drives are usually operated in what is known as the part-load range. For the above-mentioned applications of these small drives, the drive function is integrated directly into the process in the sense of a mechatronic system. The electric motor in this case becomes an integrated built-in component.
Besides these constructional boundary conditions, these small drives are to be rotational-speed-variable. By way of example, the drive can thus be converter-fed and can thus have an intermediate voltage circuit with a pulse-controlled converter. In the case of transportable devices, it is additionally possible to replace the intermediate voltage circuit with a DC voltage source, for example a battery. Particularly for applications in medical engineering, electric motors that can provide a high torque and at the same time have a low weight, a high energy efficiency, exhibit low heating and have a high balance quality are usually desirable.
In order to achieve this, permanently excited AC voltage servomotors are nowadays usually used in conjunction with a pulse converter. In the case of these electric motors, the stators are usually formed with a laminated core provided with a winding, such that, with increasing rotational speed, the magnetization losses or core losses rise dominantly. Particularly in part-load operation, the practically load-independent core losses lead to a considerable worsening of the energy efficiency. In addition, the active parts of such electric motors usually comprise components made of iron, which constitute an undesirable weight component and can lead to detent torques.
A linear motor with a secondary part having permanent magnets and with a movable primary part having multi-phase windings through which current is passed is known from EP 1 858 142 A1. To increase the attainable drive forces, the permanent magnets are arranged in such a way that their north and south poles are arranged in series and poles with the same name are arranged adjacently in the direction of movement. In addition, the coils of the multi-phase windings are formed in such a way that they surround the permanent magnets of the secondary part, at least in regions.
The principle of the linear motor described in EP 1 858 142 A1 can also be transferred to a rotary motor. Here, the rotor has a plurality of permanent magnets arranged in the circumferential direction. The stator has a winding arrangement which surrounds the permanent magnets, at least in regions. For this purpose, the stator for example has coils curved in a U-shaped manner. However, a manufacturing of these coils is very elaborate and costly, in particular with small rotor diameters.